Safety device



J. E. CARRELL April 4 11% l U i 70 5. ISOOLBS.

FIG. 4

JOHN CARRELL FIG. I

Patented Apr. 4, 1950 UNITED STATES errics (Granted under the act of March '3,v 1883, as amended April 30, 1928;. 3'70 "5. G. 757') 1 Claim.

This invention relates .to safety devices and, moreparticularly, to a new. and. improved safety locking device for control of the boom travel of boom cranes.

I Heretofore in the operation of boom cranes, it has been common to mount such cranes upon trucks and thelike so that they are portable and in such constructions the boom may swing from a position over the centerline of the truck 'toa position, far to one side of the truck in order to pick up objects and lift them onto the platform of the truck. However, it will be apparent that in such operations the load to be lifted exerts a greater tilting moment on the truck .as the boom is moved farther to one side and, for that reason, a load located to one side of the truck a considerable distance may, when lifted, cause the truck to. tilt dangerously and may perhaps cause seriousLaccident involving damage to. property and,

injury to operating personnel.

An experienced crane operator .by his knowle-v edge of the capacity of the boom crane and hence his ability to judge the weight of load whichmay safelybe handled at various distances from the center of gravity of the truck may operate the boom crane without difficulty. However, a failure in any instance to appreciate the limitations of load, which vary with the movement of the boom crane away from the center of gravity of the truck, will cause operators of less experience to have accidents with the aforesaid undesirable results.

It is, therefore, an object of the present invention to provide a safety device which indicates to the operator the load limitations which may properly be imposed upon a boom crane in use.

A further object of the present invention is to provide a safety device incorporating suitable indicia showing load capacity limitations and which limitations are automatically pointed out to the operator and serve to warn against improper operation of a boom crane.

Still another object of the present invention is to provide a new and improved safety device for control of the swing of a boom crane whereby the permissible load that may be lifted at a specified angle of swing is automatically indicated and where, in addition, the boom maysautmnatically be retained in the adjusted position without the possibility of accidental displacement during the load lifting process.

Further objects and advantages will be apparent from the following specification and appended drawings, in which latter,

v Fig. 1 is a vertical side elevation of a lift truck embodying the present invention;

Fig. 2 is a rear view of the embodiment illustrated in Fig. 1;.

, Fig. 3 is a top. plan view of the embodiment illustrated in Figs. .1 and 2; and

Fig. 4- is an enlarged detailed view of a handle 7 locking strip.

Referring. to. the drawings in detail, the em bodiment illustrated comprises a mobile truck Ill whichmay be mounted uponsui-table wheels H and I2: so that it may be moved from place to. place as desired- This truck may contain the usual prime .mover, such as an electric motor and storage batteries, so that the truck and a load to be carried may be transported about as in a warehouse, along a dock or elsewhere. Suitable provision may be made. for steering the truck in a conventional way.

The truck may include a flat portion I3 con stituting. a platform upon which goods may be carried, and, to lift heavy goods On and off this. platform, there may be. provided a boom 14 with its lower end pivoted at IE toa boom carrying turntable I6 which is vertically pivoted for rota tion about a point I! as illustrated. Point I! may be located substantially along the center line of the truck as shown in Fig. 3. Suitable winch mechanisms and turntable operating and control mechanisms of conventional design may be housed in a rearwardly extending portion N3 of the turntable.

Electric motors l9 and 20 may be mounted as shown to provide the desired load lifting power for the boom and to drive the boom in its training rotation about the pivot point H. The training movement of the boom may be controlled by a rearwardly projecting control handle 2| which, in operation, is first lifted and then swung from side to side in order to cause the appropriate electric control motor to train the boom through the desired arc of movement.

The improved safety locking device of the present invention operates in conjunction with the control handle 2| aforesaid and comprises an arcuately formed strip or plate 22 which is disposed along the path of, and underneath, the rearwardly extending handle 2|. As mentioned, the handle 2| when at rest is in its lowered position and may rest in one of the appropriate notches 23, 24, 25, 25 or 2'! in the arcuate strip 22 acccording to the station to which it is swung. Thus it will be seen that with the above arrangement and the handle 2| in down position it is locked in place and no training movement of the boom may be effected. In the event such training movement is desired, the handle 2| is first raised and it may then be manipulated sidewise to establish the proper electrical contact and energize the training motor to cause the boom to swing to the desired point. Over-travel of the boom is prevented by raised end abutments 28 constituting limit stops at each end of the arcuate plate.

As mentioned above, the lifting capacity of the boom varies with the amount of boom movement away from the center of gravity of the truck. Therefore, it is incumbent on the boom operator to use judgment in not attempting to raise or lower loads in excess of the lifting capacity at the point to which the boom is adjusted.

In order to assure that an improper load is not lifted with consequent possibility of damage to property and injury to personnel, the appropriate notches 23 to 21 inclusive may be marked with suitable indicia to show the maximum load which may safely be handled by a boom when trained to that position. Thus, when the boom is at the center position with the boom training handle 2| in notch 25 the maximum load may safely be lifted, but, as the boom is swung to one side to rest either in notch 24 or notch 26 then a lesser load may safely be lifted. The limit of the boom crane in this position may be marked adjacent to the appropriate notch, such as the 1500 lbs. illustrated in Fig. 2, and, for a boom position still farther away, the notches 23 and 21 into which the training handle falls may be appropriately marked with indicia of lesser value, such as the figure 750 lbs. illustrated in Fig. 4. Of course, in use any number of notches may be provided at intervals along the strip 22, and it is not desired to limit the present invention to the number or the particular disposition of the notches illustrated.

While a particular embodiment of the invention is shown, it will be understood, of course, that it is not desired to be limited thereto since many modifications may be made, and it is,

therefore, contemplated by the appended claim to cover any such modifications as fall within the true spirit and scope of this invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

In a device for positioning the control handle of a rotatable boom crane in an adjusted position and simultaneously indicating the load limits which may safely be imposed in said adjusted position to avoid tilting of the crane comprising, an elongated arcuate upstanding plate member having control handle receiving notches formed at spaced intervals along its arcuate upper edge, said arcuate notched plate being disposed adjacent the normal path of travel of the control handle during its movement while the boom crane is in rotation, and indicia disposed adjacent each of the spaced apart control handle receiving notches to indicate safe load limits for the cor-.

responding position of the control handle to avoid tilting of the crane, and said arcuate plate member having end abutments extending above the upper edge thereof and constituting limit stops at each end of the arcuate plate to prevent overtravel of the handle and boom.

JOHN E. CARRELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Nasset Apr. 24, 1945 

